An illumination optics for a microlithographic projection exposure apparatus is disclosed in US 2006/0072095 A1, in US 2007/0211231 A1, in US 2007/0058151 A1 and in US 2006/0158624 A1.
As far as the microlithographic production of semiconductor components and other finely structured components is concerned, the performance of projection exposure apparatuses is essentially determined by the imaging properties of the projection objectives. Moreover, the image quality, the process flexibility, the wafer throughput that is achievable using the apparatus, and other performance features are essentially determined by properties of the illumination system, i.e., the illumination optics and the radiation source, disposed upstream of the projection objective. The illumination optics should be capable of preparing the light of a primary light source such as a laser at the highest possible efficiency so as to generate the most uniform possible intensity distribution in an object or illumination field of the illumination system. Furthermore, the illumination system should be able to generate various modes of illumination so as to optimize the illumination in terms of the structures of the individual templates, in other words masks or reticles, to be imaged. Conventional setting possibilities include various conventional illumination settings having different degrees of coherence as well as annular field illuminations and dipole or quadrupole illumination. Non-conventional illumination settings for generating an oblique illumination may for instance be employed to achieve an increased depth of field using two-beam interference or an increased resolution capability. The generation of various illumination modes for the object field using the at least two beam influencing regions of the optical beam influencing element may be independent of a light attenuation. This is achievable by a diffractive, refractive or reflective generation in the beam influencing regions.
Rapid modifications of the illumination setting allowing a mask in the object field to be exposed to two different illumination settings in short intervals may be desired to perform multiple patternings. The possibilities of conventional illumination optical systems comprising variably adjustable pupil forming devices are limited in this regard, in particular if the masses of the displaceable optical components need to travel relatively long travel distances in order to switch between different illumination settings. When exchangeable pupil filters are used, this may result in light losses.